Field of the Invention
The present invention relates to a cooling structure for a bearing device, and relates to a cooling structure for a spindle of a machine tool and a bearing incorporated in the spindle, for example.
Description of Related Art
For spindle devices of machine tools, the temperature increase in the devices needs to be kept small in order to ensure the processing accuracy. However, the speed for the recent machine tools tends to increase in order to improve the processing efficiency, and the amount of heat generated from the bearing that supports the spindle also tends to increase, along with this increase in speed. The so-called motor built-in spindle devices including a driving motor incorporated therein are increasing in number, which also causes heat generation.
A temperature increase in the bearing due to heat generation results in an increased preload, and thus needs to be minimized from the viewpoint of increasing the speed and the precision of the spindle. Examples of the method for suppressing a temperature increase in the spindle device include a method in which compressed air for cooling is supplied to the bearing so as to cool the spindle and the bearing (e.g., Patent Document 1). In Patent Document 1, the spindle and the bearing are cooled by jetting cool air into the space between two bearings at an angle to the rotation direction so as to create a swirl flow.